Factual error: The sheriff and his posse raise huge dust clouds as they gallop down the road. But the stagecoach they're chasing, with four horses and four wheels, is on the same road and isn't raising any dust at all.
Continuity mistake: Curry takes his boots off and runs across a patch of very dusty, dirty desert. When he returns to put his boots back on, the white socks are perfectly clean with no dirt on them.
Continuity mistake: In the opening scenes of the chase, Heyes is wearing a vest, then not wearing a vest, then wearing a vest.